Line
Line is used to connect two areas of symmetrical telecommunications lines. Unlike the traditional PSTN, the line does not have a telephone number, and both ends of the leased line are permanently connected. Dedicated lines can be used in telephony, data and Internet services. In the UK, green rates are generally 64k, 128k, 256k, 512k, 2M, these rates are provided to users in the form of X.21. Higher rates are provided by other interfaces. In the United States, leased lines are generally available as T1 lines, based on 56k and 64k time division multiplexing. This advantage is that multiple logical lines can be transmitted on a physical line, and can be simply upgraded. But the user must manage their own network terminal device - the channel service unit or the data service unit (CSU / DSU). Dedicated lines generally refer to permanently connected data services based on circuit switched. For a variety of reasons, the green data transmission service is now being replaced by DSL switching based on packet switching and metro Ethernet. ...